I also noticed a slow using Geonear with 2dsphere index,
but what is slow, im pretty new with mongo so imnot sure ,
here is the context:
i make a full scan over 35000 item collections with no limit result,
it takes about 5s on a 1core vm google cloud machine.
If its not a normal things (i guess) , i can provide you the collection for reproduce pb;
We just discover mongo and love it but this limitation is a serious blocker for us project.